Seasonal dynamics of phytoplankton and its relationship with environmental factors in Lake Hulun

Abstract

为探究呼伦湖浮游植物群落的季节变化特征及其与环境因子的关系，本研究分别于2019年3、5—10月对呼伦湖浮游植物的种类、细胞密度和生物量及湖水水质进行调查.结果显示，共鉴定出120种浮游植物，隶属于7门72属.从浮游植物群落季节组成差异上来看，春季绿藻门种类数最多，其次是硅藻门、蓝藻门；夏秋季绿藻门种类数最多，蓝藻门次之；冬季硅藻门种类数最多，绿藻门次之.呼伦湖浮游植物优势种主要为硅藻门的梅尼小环藻（Cyclotella meneghiniana）、蓝藻门的卷曲长孢藻（Anabaena circinalis）和细小平裂藻（Merismopedia minima），种类数在春季最多，秋冬季最少.浮游植物细胞密度在春季（123.52×10⁴ cells/L）和冬季（16.41×10⁴ cells/L）较夏季（280.80×10⁴ cells/L）和秋季（380.63×10⁴ cells/L）低，春冬季绿藻门细胞密度最高，夏秋季蓝藻门细胞密度最高.就浮游植物生物量而言，夏季（0.38 mg/L）最大，其次是秋季（0.26 mg/L）和春季（0.24 mg/L），冬季（0.13 mg/L）最小.香农-威纳（Shannon-Wiener）多样性指数、均匀度指数和综合营养状态指数均表明呼伦湖水体处于中营养状态.冗余分析（RDA）表明：水温、叶绿素a、pH和营养盐浓度是影响呼伦湖浮游植物群落分布的主要环境因子.;To understand the phytoplankton community characteristics and its relationships with environmental factors, we investigated the species, abundance and biomass of phytoplankton and environmental factors at eight sampling sites in Lake Hulun during March and from May to October of 2019. The results showed that:A total of 120 phytoplankton species were identified, belonging to 7 plyla and 72 genera. In terms of the seasonal composition of the phytoplankton community, Chlorophyta was the dominant groups in spring, followed by Bacillariophyta and Cyanophyta. The number of Chlorophyta was the largest in summer and autumn, followed by Cyanophyta. Bacillariophyta was the dominant group in winter, followed by Chlorophyta. The dominant species of phytoplankton in Lake Hulun were Cyclotella meneghiniana of Bacillariophyta, Anabaena circinalis and Merismopedia minima of Cyanophyta. The number of the dominant species was the most in spring and the least in autumn and winter. The phytoplankton abundance in spring (123.52×10⁴ cells/L) and winter (16.41×10⁴ cells/L) was lower than that in summer (280.80×10⁴ cells/L) and autumn (380.63×10⁴ cells/L). The abundance of Chlorophyta was the highest in spring and winter, and the abundance of Cyanophyta was the highest in summer and autumn. In terms of phytoplankton biomass, summer (0.38 mg/L) had the largest, followed by autumn (0.26 mg/L) and spring (0.24 mg/L), and winter (0.13 mg/L) had the smallest. Shannon-Wiener diversity index, evenness index J and comprehensive trophic state index all indicated that Lake Hulun was in mesotrophic condition. Redundancy analysis of phytoplankton abundance and water environmental factors showed that water temperature, chlorophyll-a, pH and nitrogen and phosphorus nutrients were the main environmental factors that affected the distribution of the phytoplankton community in Lake Hulun.